Top port surface mount silicon condenser microphone package

ABSTRACT

The present invention relates to a surface mount package for a silicon condenser microphone and methods for manufacturing the surface mount package. The surface mount package uses a limited number of components which simplifies manufacturing and lowers costs, and features a substrate that performs functions for which multiple components were traditionally required, including providing an interior surface on which the silicon condenser die is mechanically attached, providing an interior surface for making electrical connections between the silicon condenser die and the package, and providing an exterior surface for surface mounting the package to a device&#39;s printed circuit board and for making electrical connections between package and the device&#39;s printed circuit board.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/286,558 (now U.S. Pat. No. 8,358,004), filed Nov. 1, 2011, which is acontinuation of U.S. patent application Ser. No. 13/111,537 (now U.S.Pat. No. 8,121,331), filed May 19, 2011, which is a continuation of U.S.patent application Ser. No. 11/741,881 (now U.S. Pat. No. 8,018,049),filed Apr. 30, 2007, which is a divisional of U.S. patent applicationSer. No. 10/921,747 (now U.S. Pat. No. 7,434,305), filed Aug. 19, 2004,which is a continuation-in-part of U.S. patent application Ser. No.09/886,854 (now U.S. Pat. No. 7,166,910), filed Jun. 21, 2001, whichclaims the benefit of U.S. Provisional Patent Application No.60/253,543, filed Nov. 28, 2000. U.S. patent application Ser. No.13/668,035, filed Nov. 2, 2012, U.S. patent application Ser. No.13/668,103, filed Nov. 2, 2012, U.S. patent application Ser. No.13/732,179, filed Dec. 31, 2012, U.S. patent application Ser. No.13/732,205, filed Dec. 31, 2012, U.S. patent application Ser. No.13/732,232, filed Dec. 31, 2012, and U.S. patent application Ser. No.13/732,265, filed Dec. 31, 2012, are also continuations of U.S. patentapplication Ser. No. 13/286,558 (now U.S. Pat. No. 8,358,004). Theseapplications are hereby incorporated by reference herein in theirentireties for all purposes.

TECHNICAL FIELD

This patent relates generally to a housing for a transducer. Moreparticularly, this patent relates to a silicon condenser microphoneincluding a housing for shielding a transducer.

BACKGROUND OF THE INVENTION

There have been a number of disclosures related to building microphoneelements on the surface of a silicon die. Certain of these disclosureshave come in connection with the hearing aid field for the purpose ofreducing the size of the hearing aid unit. While these disclosures havereduced the size of the hearing aid, they have not disclosed how toprotect the transducer from outside interferences. For instance,transducers of this type are fragile and susceptible to physical damage.Furthermore, they must be protected from light and electromagneticinterferences. Moreover, they require an acoustic pressure reference tofunction properly. For these reasons, the silicon die must be shielded.

Some shielding practices have been used to house these devices. Forinstance, insulated metal cans or discs have been provided.Additionally, DIPs and small outline integrated circuit (SOIC) packageshave been utilized. However, the drawbacks associated with manufacturingthese housings, such as lead time, cost, and tooling, make these optionsundesirable.

SUMMARY OF THE INVENTION

The present invention is directed to a silicon condenser microphonepackage that allows acoustic energy to contact a transducer disposedwithin a housing. The housing provides the necessary pressure referencewhile at the same time protects the transducer from light,electromagnetic interference, and physical damage. In accordance with anembodiment of the invention a silicon condenser microphone includes atransducer and a substrate and a cover forming the housing. Thesubstrate may have an upper surface with a recess formed thereinallowing the transducer to be attached to the upper surface and tooverlap at least a portion of the recess thus forming a back volume. Thecover is placed over the transducer and includes an aperture adapted forallowing sound waves to reach the transducer.

Other features and advantages of the invention will be apparent from thefollowing specification taken in conjunction with the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a first embodiment of a siliconcondenser microphone of the present invention;

FIG. 2 is a cross-sectional view of a second embodiment of a siliconcondenser microphone of the present invention;

FIG. 3 is a cross-sectional view of a third embodiment of a siliconcondenser microphone of the present invention;

FIG. 4 is a cross-sectional view of the third embodiment of the presentinvention affixed to an end user circuit board;

FIG. 5 is a cross-sectional view of the third embodiment of the presentinvention affixed to an end user circuit board in an alternate fashion;

FIG. 6 is a plan view of a substrate to which a silicon condensermicrophone is fixed;

FIG. 7 is a longitudinal cross-sectional view of a microphone package ofthe present invention;

FIG. 8 is a lateral cross-sectional view of a microphone package of thepresent invention;

FIG. 9 is a longitudinal cross-sectional view of a microphone package ofthe present invention;

FIG. 10 is a lateral cross-sectional view of a microphone package of thepresent invention;

FIG. 11 is a cross-sectional view of a top portion for a microphonepackage of the present invention;

FIG. 12 is a cross-sectional view of a top portion for a microphonepackage of the present invention;

FIG. 13 is a cross-sectional view of a top portion for a microphonepackage of the present invention;

FIG. 14 a is a cross-sectional view of a laminated bottom portion of ahousing for a microphone package of the present invention;

FIG. 14 b is a plan view of a layer of the laminated bottom portion ofFIG. 14 a;

FIG. 14 c is a plan view of a layer of the laminated bottom portion ofFIG. 14 a;

FIG. 14 d is a plan view of a layer of the laminated bottom portion ofFIG. 14 a;

FIG. 15 is a cross-sectional view of a bottom portion for a microphonepackage of the present invention;

FIG. 16 is a cross-sectional view of a bottom portion for a microphonepackage of the present invention;

FIG. 17 is a cross-sectional view of a bottom portion for a microphonepackage of the present invention;

FIG. 18 is a cross-sectional view of a bottom portion for a microphonepackage of the present invention;

FIG. 19 is a plan view of a side portion for a microphone package of thepresent invention;

FIG. 20 is a cross-sectional view of a side portion for a microphonepackage of the present invention;

FIG. 21 is a cross-sectional view of a side portion for a microphonepackage of the present invention;

FIG. 22 is a cross-sectional view of a side portion for a microphonepackage of the present invention;

FIG. 23 is a cross-sectional view of a microphone package of the presentinvention;

FIG. 24 is a cross-sectional view of a microphone package of the presentinvention;

FIG. 25 is a cross-sectional view of a microphone package of the presentinvention;

FIG. 26 is a cross-sectional view of a microphone package of the presentinvention;

FIG. 27 is a cross-sectional view of a microphone package of the presentinvention with a retaining ring;

FIG. 28 is a cross-sectional view of a microphone package of the presentinvention with a retaining wing;

FIG. 29 is a cross-sectional view of a microphone package of the presentinvention with a retaining ring;

FIG. 30 is a plan view of a panel of a plurality of microphone packages;and

FIG. 31 is a plan view of a microphone pair.

DETAILED DESCRIPTION

While the invention is susceptible of embodiments in many differentforms, there is shown in the drawings and will herein be described indetail several possible embodiments of the invention with theunderstanding that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the broad aspect of the invention to the embodimentsillustrated.

The present invention is directed to microphone packages. The benefitsof the microphone packages disclosed herein over microphone packagingutilizing plastic body/lead frames include the ability to processpackages in panel form allowing more units to be formed per operationand at much lower cost. The typical lead frame for a similarlyfunctioning package would contain between 40 and 100 devices connectedtogether. The present disclosure would have approximately 14,000 devicesconnected together (as a panel). Also, the embodiments disclosed hereinrequire minimal “hard-tooling” This allows the process to adjust tocustom layout requirements without having to redesign mold, lead frame,and trim/form tooling.

Moreover, many of the described embodiments have a better match ofthermal coefficients of expansion with the end user's PCB, typicallymade of FR-4, since the microphone package is also made primarily ofFR-4. These embodiments of the invention may also eliminate the need forwire bonding that is required in plastic body/lead frame packages. Thefootprint is typically smaller than that would be required for a plasticbody/lead frame design since the leads may be formed by plating athrough-hole in a circuit board to form the pathway to the solder pad.In a typical plastic body/lead frame design, a (gull wing configurationwould be used in which the leads widen the overall foot print.

Now, referring to FIGS. 1-3, three embodiments of a silicon condensermicrophone package 10 of the present invention are illustrated. Includedwithin silicon microphone package 10 is a transducer 12, e.g. a siliconcondenser microphone as disclosed in U.S. Pat. No. 5,870,482 which ishereby incorporated by reference and an amplifier 16. The package itselfincludes a substrate 14, a back volume or air cavity 18, which providesa pressure reference for the transducer 12, and a cover 20. Thesubstrate 14 may be formed of FR-4 material allowing processing incircuit board panel form, thus taking advantage of economies of scale inmanufacturing. FIG. 6 is a plan view of the substrate 14 showing theback volume 18 surrounded a plurality of terminal pads.

The back volume 18 may be formed by a number of methods, includingcontrolled depth drilling of an upper surface 19 of the substrate 14 toform a recess over which the transducer 12 is mounted (FIG. 1); drillingand routing of several individual sheets of FR-4 and laminating theindividual sheets to form the back volume 18, which may or may not haveinternal support posts (FIG. 2); or drilling completely through thesubstrate 14 and providing a sealing ring 22 on the bottom of the devicethat will seal the back volume 18 during surface mounting to a user's“board” 28 (FIGS. 3-5). In this example, the combination of thesubstrate and the user's board 28 creates the back volume 18. The backvolume 18 is covered by the transducer 12 (e.g., a MEMS device) whichmay be “bumpbonded” and mounted face down. The boundary is sealed suchthat the back volume 18 is operably “air-tight.”

The cover 20 is attached for protection and processability. The cover 20contains an aperture 24 which may contain a sintered metal insert 26 toprevent water, particles and/or light from entering the package anddamaging the internal components inside; i.e. semiconductor chips. Theaperture 24 is adapted for allowing sound waves to reach the transducer12. The sintered metal insert 26 will also have certain acousticproperties, e.g. acoustic damping or resistance. The sintered metalinsert 26 may therefore be selected such that its acoustic propertiesenhance the functional capability of the transducer 12 and/or theoverall performance of the silicon microphone 10.

Referring to FIGS. 4 and 5 the final form of the product is a siliconcondenser microphone package 10 which would most likely be attached toan end user's PCB 28 via a solder reflow process. FIG. 5 illustrates amethod of enlarging the back volume 18 by including a chamber 32 withinthe end user's circuit board 28.

Another embodiment of a silicon condenser microphone package 40 of thepresent invention is illustrated in FIGS. 7-10. In this embodiment, ahousing 42 is formed from layers of materials, such as those used inproviding circuit boards. Accordingly, the housing 42 generallycomprises alternating layers of conductive and non-conductive materials44, 46. The non-conductive layers 46 are typically FR-4 board. Theconductive layers 44 are typically copper. This multi-layer housingconstruction advantageously permits the inclusion of circuitry, powerand ground planes, solder pads, ground pads, capacitance layers andplated through holes pads within the structure of the housing itself.The conductive layers provide EMI shielding while also allowingconfiguration as capacitors and/or inductors to filter input/outputsignals and/or the input power supply.

In the embodiment illustrated, the housing 42 includes a top portion 48and a bottom portion 50 spaced by a side portion 52. The housing 42further includes an aperture or acoustic port 54 for receiving anacoustic signal and an inner chamber 56 which is adapted for housing atransducer unit 58, typically a silicon die microphone or a ball gridarray package (BGA). The top, bottom, and side portions 48, 50, 52 areelectrically connected, for example with a conductive adhesive 60. Theconductive adhesive may be provided conveniently in the form of suitablyconfigured sheets of dry adhesive disposed between the top, bottom andside portions 48, 50 and 52. The sheet of dry adhesive may be activatedby pressure, heat or other suitable means after the portions are broughttogether during assembly. Each portion may comprise alternatingconductive and non-conductive layers of 44, 46.

The chamber 56 may include an inner lining 61. The inner lining 61 isprimarily formed by conductive material. It should be understood thatthe inner lining may include portions of non-conductive material, as theconductive material may not fully cover the non-conductive material. Theinner lining 61 protects the transducer 58 against electromagneticinterference and the like, much like a faraday cage. The inner lining 61may also be provided by suitable electrically coupling together of thevarious conductive layers within the top, bottom and side portions 48,50 and 52 of the housing.

In the various embodiments illustrated in FIGS. 7-10 and 23-26, theportions of the housing 42 that include the aperture or acoustic port 54further include a layer of material that forms an environmental barrier62 over or within the aperture 54. This environmental barrier 62 istypically a polymeric material formed to a film, such as apolytetrafluoroethylene (PTFE) or a sintered metal. The environmentalbarrier 62 is supplied for protecting the chamber 56 of the housing 42,and, consequently, the transducer unit 58 within the housing 42, fromenvironmental elements such as sunlight, moisture, oil, dirt, and/ordust. The environmental barrier 62 will also have inherent acousticproperties, e.g. acoustic damping/resistance. Therefore theenvironmental barrier 62 is chosen such that its acoustic propertiescooperate with the transducer unit 58 to enhance the performance of themicrophone. This is particularly true in connection with the embodimentsillustrated in FIGS. 24 and 25, which may be configured to operate asdirectional microphones.

The environmental barrier layer 62 is generally sealed between layers ofthe portion, top 48 or bottom 50 in which the acoustic port 54 isformed. For example, the environmental barrier may be secured betweenlayers of conductive material 44 thereby permitting the layers ofconductive material 44 to act as a capacitor (with electrodes defined bythe metal) that can be used to filter input and output signals or theinput power. The environmental barrier layer 62 may further serve as adielectric protective layer when in contact with the conductive layers44 in the event that the conductive layers also contain thin filmpassive devices such as resistors and capacitors.

In addition to protecting the chamber 56 from environmental elements,the barrier layer 62 allows subsequent wet processing, board washing ofthe external portions of the housing 42, and electrical connection toground from the walls via thru hole plating. The environmental barrierlayer 62 also allows the order of manufacturing steps in the fabricationof the printed circuit board-based package to be modified. Thisadvantage can be used to accommodate different termination styles. Forexample, a double sided package can be fabricated having a pair ofapertures 54 (see FIG. 25), both including an environmental barrierlayer 62. The package would look and act the same whether it is mountedface up or face down, or the package could be mounted to providedirectional microphone characteristics. Moreover, the environmentalbarrier layer 62 may also be selected so that its acoustic propertiesenhance the directional performance of the microphone.

Referring to FIGS. 7, 8, and 11-13 the transducer unit 58 is generallynot mounted to the top portion 48 of the housing. This definition isindependent of the final mounting orientation to an end user's circuitboard. It is possible for the top portion 48 to be mounted face downdepending on the orientation of the transducer 58 as well as the choicefor the bottom portion 50. The conductive layers 44 of the top portion48 may be patterned to form circuitry, ground planes, solder pads,ground pads, capacitors and plated through hole pads. Referring to FIGS.1-13 there may be additional alternating conductive layers 44,non-conductive layers 46, and environmental protective membranes 62 asthe package requires. Alternatively, some layers may be deliberatelyexcluded as well. The first non-conductive layer 46 may be patterned soas to selectively expose certain features on the first conductive layer44.

FIG. 11 illustrates an alternative top portion 48 for a microphonepackage. In this embodiment, a connection between the layers can beformed to provide a conduit to ground. The top portion of FIG. 11includes ground planes and/or pattern circuitry 64 and the environmentalbarrier 62. The ground planes and or pattern circuitry 64 are connectedby pins 65.

FIG. 12 illustrates another embodiment of a top portion 48. In additionto the connection between layers, ground planes/pattern circuitry 64,and the environmental barrier 62, this embodiment includes conductivebumps 66 (e.g. Pb/Sn or Ni/Au) patterned on the bottom side to allowsecondary electrical contact to the transducer 58. Here, conductivecircuitry would be patterned such that electrical connection between thebumps 66 and a plated through hole termination is made.

FIG. 13 illustrates yet another embodiment of the top portion 48. Inthis embodiment, the top portion 48 does not include an aperture oracoustic port 54.

Referring to FIGS. 7, 8 and 14-18, the bottom portion 50 is thecomponent of the package to which the transducer 58 is primarilymounted. This definition is independent of the final mountingorientation to the end user's circuit board. It is possible for thebottom portion 50 to be mounted facing upwardly depending on themounting orientation of the transducer 58 as well as the choice for thetop portion 48 construction. Like the top portion 48, the conductivelayers 44 of the bottom portion 50 may be patterned to form circuitry,ground planes, solder pads, ground pads, capacitors and plated throughhole pads. As shown in FIGS. 14-18, there may be additional alternatingconductive layers 44, non-conductive layers 46, and environmentalprotective membranes 62 as the package requires. Alternatively, somelayers may be deliberately excluded as well. The first non-conductivelayer 46 may be patterned so as to selectively expose certain featureson the first conductive layer 44.

Referring to FIGS. 14 a through 14 d, the bottom portion 50 comprises alaminated, multi-layered board including layers of conductive material44 deposited on layers of non-conductive material 46. Referring to FIG.14 b, the first layer of conductive material is used to attach wirebonds or flip chip bonds. This layer includes etched portions to definelead pads, bond pads, and ground pads. The pads would have holes drilledthrough them to allow the formation of plated through-holes.

As shown in FIG. 14 c, a dry film 68 of non-conductive material coversthe conductive material. This illustration shows the exposed bondingpads as well as an exposed ground pad. The exposed ground pad would comein electrical contact with the conductive epoxy and form the connectionto ground of the side portion 52 and the base portion 50.

Referring to FIG. 14 d, ground layers can be embedded within the baseportion 50. The hatched area represents a typical ground plane 64. Theground planes do not overlap the power or output pads, but will overlapthe transducer 58.

Referring to FIG. 15, an embodiment of the bottom portion 50 isillustrated. The bottom portion 50 of this embodiment includes a soldermask layer 68 and alternating layers of conductive and non-conductivematerial 44, 46. The bottom portion further comprises solder pads 70 forelectrical connection to an end user's board.

FIGS. 16 and 17 illustrate embodiments of the bottom portion 50 withenlarged back volumes 18. These embodiments illustrate formation of theback volume 18 using the conductive/non-conductive layering.

FIG. 18 shows yet another embodiment of the bottom portion 50. In thisembodiment, the back portion 50 includes the acoustic port 54 and theenvironmental barrier 62.

Referring to FIGS. 7-10 and 19-22, the side portion 52 is the componentof the package that joins the bottom portion 50 and the top portion 48.The side portion 52 may include a single layer of a non-conductivematerial 46 sandwiched between two layers of conductive material 44. Theside portion 52 forms the internal height of the chamber 56 that housesthe transducer 58. The side portion 52 is generally formed by one ormore layers of circuit board material, each having a routed window 72(see FIG. 19).

Referring to FIGS. 19-22, the side portion 52 includes inner sidewalls74. The inner sidewalls 74 are generally plated with a conductivematerial, typically copper, as shown in FIGS. 20 and 21. The sidewalls74 are formed by the outer perimeter of the routed window 72 andcoated/metallized with a conductive material.

Alternatively, the sidewalls 74 may be formed by may alternating layersof non-conductive material 46 and conductive material 44, each having arouted window 72 (see FIG. 19). In this case, the outer perimeter of thewindow 72 may not require coverage with a conductive material becausethe layers of conductive material 44 would provide effective shielding.

FIGS. 23-26 illustrate various embodiments of the microphone package 40.These embodiments utilize top, bottom, and side portions 48, 50, and 52which are described above. It is contemplated that each of the top,bottom, and side portion 48, 50, 52 embodiments described above can beutilized in any combination without departing from the inventiondisclosed and described herein.

In FIG. 23, connection to an end user's board is made through the bottomportion 50. The package mounting orientation is bottom portion 50 down.Connection from the transducer 58 to the plated through holes is be madeby wire bonding. The transducer back volume 18 is formed by the backhole (mounted down) of the silicon microphone only. Bond pads, wirebonds and traces to the terminals are not shown. A person of ordinaryskilled in the art of PCB design will understand that the traces resideon the first conductor layer 44. The wire bonds from the transducer 58are be connected to exposed pads. The pads are connected to the solderpads via plated through holes and traces on the surface.

In FIG. 24, connection to the end user's board is also made through thebottom portion 50. Again, the package mounting orientation is bottomportion 50. Connection from the transducer 58 to the plated throughholes are made by wire bonding. The back volume is formed by acombination of the back hole of the transducer 58 (mounted down) and thebottom portion 50.

In FIG. 25, connection to the end user's board is also made through thebottom portion 50. Again, the package mounting orientation is bottomportion 50. Connection from the transducer 58 to the plated throughholes are made by wire bonding. With acoustic ports 54 on both sides ofthe package, there is no back volume. This method is suitable to adirectional microphone.

In FIG. 26, connection to the end user's board is made through the topportion 48 or the bottom portion 53. The package mounting orientation iseither top portion 48 down or bottom portion 50 down. Connection fromthe transducer 58 to the plated through holes is made by flip chippingor wire bonding and trace routing. The back volume 18 is formed by usingthe air cavity created by laminating the bottom portion 50 and the topportion 48 together. Some portion of the package fabrication isperformed after the transducer 58 has been attached. In particular, thethrough hole formation, plating, and solder pad definition would be doneafter the transducer 58 is attached. The protective membrane 62 ishydrophobic and prevents corrosive plating chemistry from entering thechamber 56.

Referring to FIGS. 27-29, the portion to which the transducer unit 58 ismounted may include a retaining ring 84. The retaining ring 84 preventswicking of an epoxy 86 into the transducer 58 and from flowing into theacoustic port or aperture 54. Accordingly, the shape of the retainingring 84 will typically match the shape of the transducer 58 foot print.The retaining ring 84 comprises a conductive material (e.g., 3 mil.thick copper) imaged on a non-conductive layer material.

Referring to FIG. 27, the retaining ring 84 is imaged onto anon-conductive layer. An epoxy is applied outside the perimeter of theretaining ring 84, and the transducer 58 is added so that it overlapsthe epoxy 86 and the retaining ring 84. This reduces epoxy 86 wicking upthe sides of the transducer's 58 etched port (in the case of a silicondie microphone).

Alternatively, referring to FIG. 28, the retaining ring 84 can belocated so that the transducer 58 does not contact the retaining ring84. In this embodiment, the retaining ring 84 is slightly smaller thanthe foot print of the transducer 58 so that the epoxy 86 has arestricted path and is, thus, less likely to wick. In FIG. 29, theretaining ring 84 is fabricated so that it contacts the etched port ofthe transducer 58. The following tables provide an illustrative exampleof a typical circuit board processing technique for fabrication of thehousing of this embodiment.

TABLE 1 Materials Material Type Component Note 1 0.5/0.5 oz. DST BottomPortion Cu 5 core FR-4 (Conductive Layers Non- Conductive Layer 1) 20.5/0.5 oz. DST Bottom Portion Cu 5 core FR-4 (Conductive Layers 3 and4; Non-Conductive Layer 2) 3 106 pre-preg For Laminating Material 1 andMaterial 2 4 0.5/0.5 oz. DST Side Portion Metallized Cu 40 Core FR-4Afterward 5 Bare/0.5 oz. Cu 2 Top Portion (Each Piece core FR-4 (2Includes 1 Conductive and 1 pieces) Non-Conductive Layer) 6 ExpandedPTFE Environmental Barrier

TABLE 2 Processing of Materials (Base Portion Material 1) Step TypeDescription Note 1 Dry Film Conductive Layers 2 Expose Mask Material 1(Upper Forms Ground Conductive Layer) Plane on Lower Conductive Layer 3Develop 4 Etch Cu No Etching on Upper Conductive Layer 5 Strip Dry Film

TABLE 3 Processing of Materials (Bottom Portion Material 2) Step TypeDescription Note 1 Dry Film Conductive Layers 2 Expose Mask Material 2(Upper Forms Ground Conductive Layer) Plane on Upper Conductive Layer 3Develop 4 Etch Cu No Etching on Upper Conductive Layer 5 Strip Dry Film

TABLE 4 Processing of Materials 1, 2, and 3 (Form Bottom Portion) StepType Description Note 1 Laminate Materials 1 and 2 Laminated UsingMaterial 3 2 Drill Thru Holes Drill Bit = 0.025 in. 3 Direct Plates ThruHoles Metallization/Flash Copper 4 Dry Film (L1 and L4) 5 Expose MaskLaminated Forms Traces and Solder Materials 1 and 2 Pads (Upper andLower Conductive Layers) 6 Develop 7 Electrolytic Cu 1.0 mil 8Electrolytic Sn As Required 9 Strip Dry Film 10 Etch Cu 11 Etch Cu 12Insert Finishing NG Option (See NG Option for Proof Option Here TableBelow) of Principle 13 Dry Film (cover 2.5 mil Minimum Thickness lay) onUpper on Upper Conductive Conductive Layer Layer Only 14 Expose MaskLaminated This mask defines an Materials 1 and 2 area on the upper(upper and lower) conductive layer that will receive a dry film soldermask (cover lay). The bottom layer will not have dry film applied to it.The plated through holes will be bridged over by the coating on the top.15 Develop 16 Cure Full Cure 17 Route Panels Route Bit = As Forms 4″ x4″ pieces. Required Conforms to finished dims

Table 5 describes the formation of the side portion 52. This processinvolves routing a matrix of openings in FR-4 board. However, punchingis thought to be the cost effective method for manufacturing. Thepunching may done by punching through the entire core, or,alternatively, punching several layers of no-flow pre-preg and thin corec-stage which are then laminated to form the wall of proper thickness.

After routing the matrix, the board will have to be electroless or DMplated. Finally, the boards will have to be routed to match the bottomportion. This step can be done first or last. It may make the piece moreworkable to perform the final routing as a first step.

TABLE 5 Processing of Material 4 (Side Portion) Step Type DescriptionNote 1 Route/Punch Route Bit = 0.031 in. Forms Side Portion Matrix ofOpenings 2 Direct 0.25 mil minimum Forms Sidewalls Metallization/ onSide Portion Flash Cu 3 Route Panels

Table 6 describes the processing of the top portion. The formation ofthe top portion 48 involves imaging a dry film cover lay or liquidsolder mask on the bottom (i.e. conductive layer forming the innerlayer. The exposed layer of the top portion 48 will not have a coppercoating. It can be processed this way through etching or purchased thisway as a one sided laminate.

A matrix of holes is drilled into the lid board. Drilling may occurafter the imaging step. If so, then a suitable solder mask must bechosen that can survive the drilling process.

TABLE 6 Processing of Top Portion Step Type Description Note 1 Dry FilmConductive Layer 2 Expose Mask Bare Layer Form Conduction Ring 3 Develop4 Cure 5 Drill Matrix Drill Bit 0.025 in. Acoustic Ports of Holes 6Laminate PTFE (Environmental Forms Top Portion Barrier) Between 2 Piecesof Material 5

TABLE 7 Processing of Laminated Materials 1 and 2 with Material 4 StepType Description Note 1 Screen Conductive Adhesive on Material 4 2Laminate Bottom Portion with Side Forms Bottom Portion Portion with SidePortion (spacer) 3 Add Transducer Silicon Die Microphone Assembly andIntegrated Circuit

TABLE 8 Processing of Laminated Materials 1, 2, and 4 with Material 5Step Type Description Note 1 Screen Conductive Adhesive on Top Portion 2Laminate Bottom Portion and Side Forms Housing Portion with Top Portion3 Dice

TABLE 9 Finishing Option NG (Nickel/Gold) Step Type Description Note 1Immersion Ni (40-50 μ-in) 2 Immersion Au (25-30 μ-in)

TABLE 10 Finishing Option NGT (Nickel/Gold/Tin) Step Type 1 Mask L2(using thick dry film or high tack dicing tape) 2 Immersion Ni (40-50μ-in) 3 Immersion Au (25-30 μ-in) 4 Remove Mask on L2 5 Mask L1 (usingthick dry film or high tack dicing tape) bridge over cavity created bywall 6 Immersion Sn (100-250 μ-in) 7 Remove Mask on L1

TABLE 11 Finishing Option ST (Silver/Tin) Step Type 1 Mask L2 (usingthick dry film or high tack dicing tape) 2 Immersion Ag (40-50 μ-in) 3Remove Mask on L2 4 Mask L1 (using thick dry film or high tack dicingtape) bridge over cavity created by wall 5 Immersion Sn (100-250 μ-in) 6Remove Mask on L1

FIG. 30 is a plan view illustrating a panel 90 for forming a pluralityof microphone packages 92. The microphone packages 92 are distributed onthe panel 90 in a 14×24 array, or 336 microphone packages total. Feweror more microphone packages may be disposed on the panel 90, or onsmaller or larger panels. As described herein in connection with thevarious embodiments of the invention, the microphone packages include anumber of layers, such as top, bottom and side portions of the housing,environmental barriers, adhesive layers for joining the portions, andthe like. To assure alignment of the portions as they are broughttogether, each portion may be formed to include a plurality of alignmentapertures 94. To simultaneously manufacture several hundred or evenseveral thousand microphones, a bottom layer, such as described herein,is provided. A transducer, amplifier and components are secured atappropriate locations on the bottom layer corresponding to each of themicrophones to be manufactured. An adhesive layer, such as a sheet ofdry adhesive is positioned over the bottom layer, and a sidewall portionlayer is positioned over the adhesive layer. An additional dry adhesivelayer is positioned, followed by an environmental barrier layer, anotherdry adhesive layer and the top layer. The dry adhesive layers areactivated, such as by the application of heat and/or pressure. The panelis then separated into individual microphone assemblies using knownpanel cutting and separating techniques.

The microphone, microphone package and method of assembly hereindescribed further allow the manufacture of multiple microphone assembly,such as microphone pairs. In the simplest form, during separation twomicrophones may be left joined together, such as the microphone pair 96shown in FIG. 31. Each microphone 98 and 100 of the microphone pair 96is thus a separate, individually operable microphone in a single packagesharing a common sidewall 102. Alternatively, as described herein,conductive traces may be formed in the various layers of either the topor bottom portion thus allowing multiple microphones to be electricallycoupled.

While specific embodiments have been illustrated and described, numerousmodifications come to mind without significantly departing from thespirit of the invention, and the scope of protection is only limited bythe scope of the accompanying Claims.

What is claimed is:
 1. A solder reflow surface mount microelectromechanical system (MEMS) microphone device comprising: a substrate comprising multiple layers of non-conductive material, each layer having a predetermined coefficient of thermal expansion, and the substrate having a planar upper surface and a planar lower surface, the upper surface having an interior region and a peripheral region that completely surrounds the interior region, the substrate further comprising: a first plurality of metal pads formed on the upper surface of the substrate; a second plurality of metal pads formed on the lower surface of the substrate and arranged within a perimeter of the lower surface of the substrate, wherein the second plurality of metal pads are configured to mechanically attach and electrically couple the surface mount MEMS microphone device to pads on a surface of an external printed circuit board; and one or more electrical traces formed completely within the substrate, wherein the traces electrically couple one or more of the first plurality of metal pads on the upper surface of the substrate to one or more of the second plurality of metal pads on the lower surface of the substrate; a MEMS microphone die mounted to the upper surface of the substrate and electrically coupled to at least one of the first plurality of metal pads on the upper surface of the substrate, wherein the acoustic passage positions a diaphragm of the MEMS microphone die away from the upper surface of the substrate; and a single-piece cover having a predetermined shape that comprises a top region having a port that passes completely through the cover, and a substantially vertical sidewall region that adjoins the central region at a substantially perpendicular angle and that completely surrounds and supports the top region, the sidewall region having a predetermined height, an exterior sidewall surface, an interior sidewall surface, and a bottom surface, wherein the bottom surface of the sidewall region is aligned with and attached to the peripheral region of the upper surface of the substrate, and wherein the predetermined shape of the cover and the predetermined height of the sidewall region, in cooperation with the interior region of the upper surface of the substrate, forms a protective enclosure for the MEMS microphone die and defines an acoustic chamber for the MEMS microphone die.
 2. A surface mount MEMS microphone device according to claim 1, wherein the one or more electrical traces are electrically coupled to one or more of the first plurality of metal pads or to one or more of the second plurality of metal pads with through-hole connections.
 3. A surface mount MEMS microphone device according to claim 1, further comprising a metal pad formed on the upper surface of the substrate, wherein the MEMS microphone die is mounted to the metal pad.
 4. A surface mount MEMS microphone device according to claim 1, wherein the non-conductive material is FR-4 material.
 5. A surface mount MEMS microphone device according to claim 1, further comprising at least one passive electrical device formed within the substrate.
 6. A surface mount MEMS microphone device according to claim 1, wherein the enclosure protects the MEMS microphone die from at least one of light, electromagnetic interference, and physical damage.
 7. A surface mount MEMS microphone device according to claim 1, wherein the enclosure further comprises acoustic material that substantially blocks environmental contaminants from entering the acoustic chamber through the port.
 8. A surface mount MEMS microphone device according to claim 1, wherein the diaphragm of the MEMS microphone die defines a front volume and a back volume in the acoustic chamber, and the port formed in the cover is acoustically coupled to the front volume, and the acoustic passage of the MEMS microphone die and the upper surface of the substrate define a back volume.
 9. A surface mount microelectromechanical system (MEMS) microphone device comprising: a printed circuit board comprising multiple layers of non-conductive material, each layer having a predetermined coefficient of thermal expansion and the printed circuit board having a planar upper surface and a planar lower surface, the upper surface having an interior region and a peripheral region that completely surrounds the interior region, the printed circuit board comprising: a first plurality of metal pads formed on the upper surface of the printed circuit board; a second plurality of metal pads formed on the lower surface of the printed circuit board and arranged within a perimeter of the lower surface of the printed circuit board, wherein the second plurality of metal pads are configured to mechanically attach and electrically couple the surface mount MEMS microphone device to pads on a surface of an external printed circuit board; and one or more circuit traces formed completely within the printed circuit board, wherein the circuit traces electrically couple one or more of the first plurality of metal pads on the upper surface of the printed circuit board to one or more of the second plurality of metal pads on the lower surface of the printed circuit board, wherein the circuit traces are patterned in at least one conductive layer interposed between the multiple layers of non-conductive material; a MEMS microphone die having an acoustic passage and mounted to the upper surface of the printed circuit board and electrically coupled to at least one of the first plurality of metal pads on the upper surface of the printed circuit board, wherein the acoustic passage positions a diaphragm of the MEMS microphone die away from the upper surface of the substrate; and a single-piece cover having a predetermined shape that comprises a top region having a port that passes completely through the cover, and a substantially vertical sidewall region that adjoins the central region at a substantially perpendicular angle and that completely surrounds and supports the top region, the sidewall region having a predetermined height, an exterior sidewall surface, an interior sidewall surface, and a bottom surface, wherein the bottom surface of the sidewall region is aligned with and mechanically attached to the peripheral region of the upper surface of the printed circuit board, and wherein the predetermined shape of the cover and the predetermined height of the sidewall region, in cooperation with the interior region of the upper surface of the printed circuit board, forms a protective enclosure for the MEMS microphone die and defines an acoustic chamber for the MEMS microphone die, wherein the cover has a first length and a first width, and the printed circuit board has a second length and a second width, and wherein the first length of the cover and second length of the printed circuit board are substantially equal, and the first width of the cover and second width of the printed circuit board are substantially equal.
 10. A surface mount MEMS microphone device according to claim 9, wherein the one or more circuit traces are electrically coupled to one or more of the first plurality of metal pads or to one or more of the second plurality of metal pads with through-hole connections.
 11. A surface mount MEMS microphone device according to claim 9, further comprising a metal pad formed on the upper surface of the printed circuit board, wherein the MEMS microphone die is mounted to the metal pad.
 12. A surface mount MEMS microphone device according to claim 9, wherein the non-conductive material is FR-4 material.
 13. A surface mount MEMS microphone device according to claim 9, further comprising at least one passive electrical device formed within the printed circuit board.
 14. A surface mount MEMS microphone device according to claim 9, wherein the enclosure protects the MEMS microphone die from at least one of light, electromagnetic interference, and physical damage.
 15. A surface mount MEMS microphone device according to claim 9, wherein the enclosure further comprises acoustic material that substantially blocks environmental contaminants from entering the acoustic chamber through the port.
 16. A surface mount MEMS microphone device according to claim 9, wherein the diaphragm of the MEMS microphone die defines a front volume and a back volume in the acoustic chamber, and the port formed in the cover is acoustically coupled to the front volume, and the acoustic passage of the MEMS microphone die and the upper surface of the substrate define a back volume.
 17. A surface mount microelectromechanical system (MEMS) microphone device comprising: a substrate comprising multiple layers of non-conductive material, each layer having a predetermined coefficient of thermal expansion, and the substrate having a planar upper surface and a planar lower surface, the upper surface having an interior region and a peripheral region that completely surrounds the interior region, the substrate further comprising: a first plurality of metal pads formed on the upper surface of the substrate; a second plurality of metal pads formed on the lower surface of the substrate and arranged within a perimeter of the lower surface of the substrate, wherein the second plurality of metal pads are configured to mechanically attach and electrically couple the surface mount MEMS microphone device to pads on a surface of an external printed circuit board; and one or more wiring traces formed completely within the substrate, wherein the wiring traces electrically couple one or more of the first plurality of metal pads on the upper surface of the substrate to one or more of the second plurality of metal pads on the lower surface of the substrate, wherein the wiring traces are patterned in at least one conductive layer interposed between the multiple layers of non-conductive material; a MEMS microphone die having an acoustic passage physically coupled to the upper surface of the substrate and electrically coupled to at least one of the first plurality of metal pads on the upper surface of the substrate, wherein the acoustic passage positions a diaphragm of the MEMS microphone die away from the upper surface of the substrate; and a single-piece cover having a predetermined shape that comprises a central region having a port that passes completely through the cover, and a substantially vertical sidewall region that adjoins the central region and that completely surrounds and supports the central region, the sidewall region having a predetermined height, an exterior surface, an interior surface, and a bottom surface, wherein the bottom surface of the sidewall region is aligned with and physically coupled to the peripheral region of the upper surface of the substrate, thereby forming a protective enclosure for the MEMS microphone die, and wherein the interior of the protective enclosure is an acoustic chamber having a volume defined by the predetermined height of sidewall region, the predetermined shape of the cover, and the width and length of the central region of the cover.
 18. A surface mount MEMS microphone device according to claim 17, wherein the one or more wiring traces are electrically coupled to one or more of the first plurality of metal pads or to one or more of the second plurality of metal pads with through-hole connections.
 19. A surface mount MEMS microphone device according to claim 17, further comprising a metal pad formed on the upper surface of the substrate, wherein the MEMS microphone die is physically coupled to the metal pad.
 20. A surface mount MEMS microphone device according to claim 17, wherein the non-conductive material is FR-4 material.
 21. A surface mount MEMS microphone device according to claim 17, further comprising at least one passive electrical device formed within the substrate.
 22. A surface mount MEMS microphone device according to claim 17, wherein the enclosure protects the MEMS microphone die from at least one of light, electromagnetic interference, and physical damage.
 23. A surface mount MEMS microphone device according to claim 17, wherein the enclosure further comprises acoustic material that substantially blocks environmental contaminants from entering the acoustic chamber through the port.
 24. A surface mount MEMS microphone device according to claim 17, wherein the diaphragm of the MEMS microphone die defines a front volume and a back volume in the acoustic chamber, and the port formed in the cover is acoustically coupled to the front volume, and the acoustic passage of the MEMS microphone die and the upper surface of the substrate define a back volume.
 25. A surface mount microelectromechanical system (MEMS) microphone device comprising: a printed circuit board having a multi-layer core of conductive and non-conductive materials wherein the non-conductive material has a predetermined coefficient of thermal expansion, and, wherein the printed circuit board has a planar upper surface and a planar lower surface, the upper surface having an interior region and a peripheral region that completely surrounds the interior region, the printed circuit board further comprising: a first metal layer formed on the upper surface of the printed circuit board and patterned into a first plurality of metal pads, wherein at least one pad of the first plurality of metal pads is formed in the peripheral region of the upper surface of the printed circuit board; a second metal layer formed on the lower surface of the printed circuit board and patterned into a second plurality of metal pads, the second plurality of metal pads arranged within a perimeter of the lower surface of the printed circuit board, wherein the second plurality of metal pads are configured to mechanically couple and electrically couple the surface mount MEMS microphone device to pads on a surface of an external printed circuit board; and one or more wiring traces formed completely within the printed circuit board, wherein the wiring traces electrically couple one or more of the first plurality of metal pads on the upper surface of the printed circuit board to one or more of the second plurality of metal pads on the lower surface of the printed circuit board, wherein the wiring traces are patterned in at least one conductive material interposed between two layers of non-conductive material; a MEMS microphone die having an acoustic passage physically coupled to the upper surface of the multi-layer printed circuit board and electrically coupled to at least one of the first plurality of patterned metal pads, wherein the acoustic passage positions a diaphragm of the MEMS microphone die away from the upper surface of the substrate; and a single-piece cover having a predetermined shape that comprises a central region having a port that passes completely through the cover, and a substantially vertical sidewall region that adjoins the central region and that completely surrounds and supports the central region, the sidewall region having a predetermined height, an exterior surface, an interior surface, and a bottom surface, wherein the bottom surface of the sidewall region is aligned with and physically coupled to the peripheral region of the upper surface of the printed circuit board, thereby forming a protective enclosure for the MEMS microphone die, and wherein the interior of the protective enclosure is an acoustic chamber having a volume defined by the predetermined height of sidewall region, the predetermined shape of the cover, and the width and length of the central region of the cover.
 26. A surface mount MEMS microphone device according to claim 25, further comprising a metal pad formed on the upper surface of the printed circuit board, wherein the MEMS microphone die is physically coupled to the metal pad.
 27. A surface mount MEMS microphone device according to claim 25, further comprising at least one passive electrical device formed within the printed circuit board.
 28. A surface mount MEMS microphone device according to claim 25, wherein the enclosure protects the MEMS microphone die from at least one of light, electromagnetic interference, and physical damage.
 29. A surface mount MEMS microphone device according to claim 25, wherein the enclosure further comprises acoustic material that substantially blocks environmental contaminants from entering the acoustic chamber through the port.
 30. A surface mount MEMS microphone device according to claim 25, wherein the diaphragm of the MEMS microphone die defines a front volume and a back volume in the acoustic chamber, and the port formed in the cover is acoustically coupled to the front volume, and the acoustic passage of the MEMS microphone die and the upper surface of the substrate define a back volume. 